When Sam Puttick was struck by a car on a summer's day four years ago, doctors warned his parents that his injuries were catastrophic. For nine months, Neil and Kazumi Puttick nursed their paralysed son in intensive care, driven by a single goal – to get him home and dedicate themselves to his recovery.

The depth of that dedication was extraordinary. The couple converted a Wiltshire farmhouse into a one-person hospital where Sam, who suffered the devastating spinal injury that paralysed him from the neck down when he was just 16 months old, could receive 24-hour care that included constant ventilation necessary to keep his lungs functioning.

Through a charity appeal, the family raised £30,000 to buy specialist equipment. Mr Puttick, a former finance manager who had worked in London and Tokyo, gave up his job two years ago to help his Japanese wife and two full-time nurses look after his son as he began school.

By January of this year, the family had overcome their trauma and settled into a new life in which Sam was thriving. Mr Puttick, 34, wrote on the appeal website stuff4sam: "I am a dad who just wants to see my son grow healthy and happy. You have given us as a family a chance to see our son grow, despite the accident, into the same person he would always have been."

Then the Putticks were once more robbed of hope and, ultimately, their will to live. Last Tuesday, Sam was admitted to intensive care at Bristol's Royal Hospital for Children with an infection diagnosed as Pneumococcal meningitis. His parents were told the illness was so severe that there was no hope of recovery for their five-year-old boy and the Putticks asked to be allowed to take him home to die.

At 8pm last Friday, a doctor was called to the family home at Wishing Well Farm in the hamlet of Brokerswood, 25 miles south-east of Bristol, and Sam was declared dead. Within 48 hours, his parents, grief-stricken beyond endurance, had joined him.

On Sunday evening, the family's silver Volkswagen people carrier, adapted to carry Sam's wheelchair, pulled into the car park about 180 metres from the cliff edge at Beachy Head in East Sussex, a notorious suicide spot 100 miles from the Putticks' home.

The couple had placed Sam's body inside a rucksack and carried another backpack which was filled with his favourite toys, a tractor and some teddy bears. It is likely they appeared to any passers-by as another pair of hikers walking through the nature reserve on the South Downs.

They made it to the top of the 500ft drop above the Belle Tout lighthouse without encountering members of the Beachy Head Chaplaincy Team, which regularly patrols the beauty spot to try to counsel anyone who seems at risk of jumping.

A Coastguard patrol spotted their bodies about 8pm on Sunday, lying on a ledge 400ft from the cliff edge. It was only when a climbing team reached them on Monday morning that the rucksack containing Sam's body was found alongside them. Sussex Police said the deaths were nothing other than an awful tragedy. Bath and North East Somerset NHS Trust said it was normal policy to allow parents of a terminally ill child to return home to allow the child to die with appropriate medical care.

Friends of the family spoke glowingly of the attention that the couple, who are understood to have met in Japan, gave to Sam, and their determination to minimise the impact of his disabilities on his life.

Sue Capon, the owner of the Brokerswood Country Park opposite the Putticks' large farmhouse, had become a close friend of the family since they moved in two years ago, giving them a pass so they could visit the park at any time. Mrs Capon said: "We are all absolutely devastated. Sam was adorable, a delight and I feel privileged to have been close to him during his short life. He never complained, he was always happy and full of smiles. He loved tractors and the chickens.

"Neil and Kazumi gave 110 per cent to Sam. Their life was Sam and without him their life did not mean anything to them. They were devoted to one another as well as to their child and it's just such a sad ending."

In the aftermath of the 2005 accident, the Putticks moved to Wishing Well Farm and submitted a planning application to convert the property to accommodate Sam. The plans included an extension with a special play area and a generator to provide emergency power for the ventilation machines Sam needed to live. The work was completed two weeks ago.

The desire to give Sam as normal a life as possible saw him start at Westbury Leigh Primary School in September. Headteacher Mary Murray said it had been a "real privilege" to have Sam in the school. Despite the severity of his condition, Sam retained a sharp intellect, according to friends. The Putticks posted videos of their son on YouTube, showing him using state-of-the-art cycling and walking machines while talking and singing with his parents.

In a website posting in September 2006, Mr Puttick, who had been running an interior design business before giving up work and had also been employed by the Royal National Institute for the Blind, wrote: "Sam is quadriplegic and can't breathe as a result of the car accident. He was a normal, healthy, active boy before but because of someone's careless driving, he is now as he is.

"We are so very proud of how he has survived, who he now is and how he continues to smile and be so damn strong in spite of everything. He is simply amazing."

The fundraising programme co-ordinated by the Putticks and their friends, which ranged from a sponsored row along the length of the Thames to dog-sledding in the Arctic, was closed earlier this year after the family said they had proved to the authorities that the equipment it paid for was critical to Sam's ongoing care. The Putticks said they would instead dedicate their efforts to raising awareness of spinal injuries.

In the stuff4sam website last night, family and friends paid tribute to the couple: "We are all better for knowing them and Sam could not have wished for better parents."